1. Field of the Invention
The present invention relates to the preparation of polymers or copolymers, i.e., (co)polymers, essentially of the acrylic, methacrylic or styrene type, which are soluble in their starting monomer or comonomer compositions, by suspended emulsion polymerization of such corresponding monomer or monomers.
2. Description of the Prior Art
By "suspended emulsion polymerization" is intended a polymerization, in the presence of an initiator system, at least one of the constituents of which is soluble in water, of at least one monomer in an aqueous phase dispersed in finely divided form.
In general, suspended emulsion polymerization may be carried out in the event that the monomer or monomers may be polymerized in emulsion, since the polymerization is conducted within the discontinuous aqueous phase and proceeds by progressive dissolution of the monomer, which forms the continuous phase of the reaction mixture.
According to the solubility or the insolubility of the (co)polymer (formed in the aqueous phase in the form of a latex) in the (co)monomer phase, two techniques are distinguished:
(1) In the event that the (co)polymer is insoluble in its (co)monomer composition (for example, in the case of PVC and PAN), the polymer precipitates and remains in the droplet of particles having a spherical appearance. This technique is described in French Patents Nos. 69/01,008, 69/37,326, 69/37,327, and 87/03,636.
(2) In the event that the (co)polymer is soluble in the (co)monomer phase, the reaction product is a mixture of a solution of (co)polymer in its (co)monomer composition and the aqueous initiating phase. The recovery of the polymer then proceeds via a costly treatment of such mixture (precipitation, drying, and the like).